T. Rowe Price holds 6.16M IONS shares (NYSE: IONS) — 3.7% stake

Rhea-AI Filing Summary

T. Rowe Price Investment Management, Inc. reports beneficial ownership of 6,159,027 shares of Ionis Pharmaceuticals common stock, representing 3.7% of the class. The filing states sole voting power over 6,140,820 shares and sole dispositive power over 6,159,027 shares.

The filing is an amendment (Schedule 13G/A, Amendment No. 5) signed on 05/15/2026 and includes a statement that the filer denies beneficial ownership for the securities referenced. The CUSIP is 462222100 and the issuer is Ionis Pharmaceuticals, Inc.

Insights

Institutional Ownership Analyst

T. Rowe Price is disclosed as holding 6.16M shares (3.7%) of IONS.

The Schedule 13G/A amendment lists 6,159,027 shares beneficially owned with 6,140,820 shares subject to sole voting power as of the filing. The form updates institutional ownership disclosure rather than announcing a transaction or change in control.

Ownership statements like this affect public registers and shareholder visibility; subsequent filings or transactions would clarify any change in position. The filing notes a denial of beneficial ownership in its affirmation language.

Key Figures

Filing type: Schedule 13G/A (Amendment No. 5) Beneficially owned: 6,159,027 shares Percent of class: 3.7% +3 more

6 metrics

Filing type Schedule 13G/A (Amendment No. 5) Ownership disclosure amendment

Beneficially owned 6,159,027 shares Amount reported in Item 4

Percent of class 3.7% Percent of class reported in Item 4

Sole voting power 6,140,820 shares Sole power to vote or direct vote

Sole dispositive power 6,159,027 shares Sole power to dispose or direct disposition

Signature date 05/15/2026 Date signed by Ellen York, Vice President

Key Terms

Schedule 13G/A, Beneficially owned, Sole dispositive power

3 terms

Schedule 13G/A regulatory

"Schedule 13G/A (Amendment No. 5) reporting beneficial ownership"

A Schedule 13G/A is an amended public filing with the U.S. securities regulator that updates a previous Schedule 13G, disclosing when an individual or group holds a substantial (typically over 5%) stake in a company and is claiming a passive, non‑controlling intent. Investors monitor these updates because rising or falling holdings can signal changing confidence, potential future moves, or shifts in voting power — like watching a public ledger where large shareholders quietly adjust their positions.

Beneficially owned financial

"Amount beneficially owned: 6159027"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

Sole dispositive power regulatory

"Sole power to dispose or to direct the disposition of: 6159027"

Sole dispositive power is the exclusive legal authority to decide what happens to a security — for example, whether to sell, transfer, or retain shares — without needing anyone else’s permission. Investors care because it signals who truly controls the economic outcome of an investment: like holding the only key to a safe, the holder can realize gains or losses and may trigger regulatory reporting, insider rules, or influence over corporate ownership.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 5)

IONIS PHARMACEUTICALS INC

(Name of Issuer)

COMMON STOCK

(Title of Class of Securities)

462222100

(CUSIP Number)

03/31/2026

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 462222100

1

Names of Reporting Persons

T. Rowe Price Investment Management, Inc.

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

MARYLAND

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 6,140,820.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 6,159,027.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

6,159,027.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

3.7 %

12

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13G

Item 1.
(a)	Name of issuer: IONIS PHARMACEUTICALS INC
(b)	Address of issuer's principal executive offices: 2855 GAZELLE COURT, CARLSBAD, CA, 92010
Item 2.
(a)	Name of person filing: T. Rowe Price Investment Management, Inc.
(b)	Address or principal business office or, if none, residence: 1307 Point Street, Baltimore, MD 21231
(c)	Citizenship: Maryland
(d)	Title of class of securities: COMMON STOCK
(e)	CUSIP No.: 462222100
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: 6159027
(b)	Percent of class: 3.7 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 6140820
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 6159027
	(iv) Shared power to dispose or to direct the disposition of: 0
Item 5.	Ownership of 5 Percent or Less of a Class.
	Ownership of 5 percent or less of a class
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	Not Applicable
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11. T. Rowe Price Investment Management, Inc. hereby declares and affirms that the filing of Schedule 13G shall not be construed as an admission that Price Investment Management is the beneficial owner of the securities referred to, which beneficial ownership is expressly denied.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

T. Rowe Price Investment Management, Inc.

Signature:	Ellen York
Name/Title:	Vice President
Date:	05/15/2026

FAQ

What stake does T. Rowe Price report in IONS?

T. Rowe Price reports beneficial ownership of 6,159,027 shares of Ionis Pharmaceuticals, representing 3.7% of the class. The filing lists voting and dispositive powers for these shares on 05/15/2026.

Does the filing show who controls voting for those IONS shares?

Yes. The filing states T. Rowe Price has sole voting power over 6,140,820 shares and sole dispositive power over 6,159,027 shares, as shown in the Schedule 13G/A amendment.

Is this a purchase or sale transaction for IONS shares?

This Schedule 13G/A amendment is an ownership disclosure and does not report a specific buy or sell transaction. It updates beneficial ownership figures and power over shares as reported on the form.

What does the filing's denial of beneficial ownership mean?

The filer includes a statement denying beneficial ownership, indicating the filer disclaims being the beneficial owner of the securities referenced. The form still discloses voting and dispositive powers and share counts as required.

Which CUSIP and issuer are referenced in the filing?

The filing references Ionis Pharmaceuticals, Inc. common stock with CUSIP 462222100. The issuer's principal executive office is listed at 2855 Gazelle Court, Carlsbad, CA.